This invention relates to monolithic flat panel display apparatus and methods for fabrication thereof and more particularly to techniques for metalizing portions of the large number of finely spaced conductors present in electro optical display apparatus to allow driver circuitry to be wire bounded thereto and the resulting electro-optical display apparatus obtained through the use of such techniques.
The difficulty of providing a large number of connections to finely spaced conductors has become legend with respect to large scale integrated circuits (LSI) and even more pronounced with respect to very large scale integrated circuit devices (VLSI). Difficulties there encountered become even more extreme when one considers the connection requirements associated with the fabrication of monolithic flat panel display apparatus such as electrophoretic display panels.
In devices of this type such as described in U.S. application Ser. No. 670,571, now U.S. Pat. No. 4,655,897, as entitled "Electrophoretic Display Panels and Associated Methods" as filed on Nov. 13, 1984 in the names of Frank J. DiSanto, Sr. and Denis A. Krusos, the inventors herein, and assigned to the assignee herein, as well as in U.S. application Ser. No. 799,458 entitled "Electrophoretic Display Panel Apparatus and Methods Therefor" as filed on Nov. 19, 1985 in the names of the instant inventors and assigned to the present assignee, resolution of 200 lines per inch is obtained in a display having a conductor density of 200 lines per inch in each of the row and column directions. Thus, in a typical display having dimensions which correspond to the typical dimensions of an 81/2 by 11 inch sheet of paper 2200 row conductors and 1700 vertically disposed column conductors would be utilized. Each conductor in the 2200 by 1700 conductor matrix formed requires connection to driver circuitry and resolution surpassing more than 200 lines per inch is envisioned.
The row and column conductors of such displays are typically etched upon the glass layer forming the display as such fine line patterns are not available through the use of other techniques. When the display is assembled, each of the 2200 row conductors and 1700 column conductors are brought out to the periphery of the panel formed where connection is typically made to driver circuits for selectively energizing the rows and columns to form patterns in accordance with data to be displayed. Typically, individual driver circuits in the form of integrated circuits are employed to drive a designated group of conductors from the periphery of the column and row. In this vein a typical driver circuit is capable of driving 64 individual conductors where the driver circuit receives 10 inputs provided by electronics external to the electrophoretic panel.
Connection to the driver circuits at the periphery of the electrophoretic panel is preferably achieved during the fabrication of the panel since alignment problems can occur due to the conductor densities involved. In such an arrangement each group of 64 row and column conductors may be specially configured at the periphery of the display to accommodate connection to specific driver chips; however, the entire assembly process is time consuming and costly. The assembly process also is typically subject to alignment errors and is often attended by reliability problems.
One technique for achieving suitable connection of the row and column conductors present in a high resolution electrophoretic display is set forth in U.S. Pat. No. 4,598,960 which is entitled "Methods and Apparatus for Connecting Closely Spaced Large Conductor Arrays Employing Multiconductor Carrier Boards" and issued on July 8, 1986 to the inventors herein and is commonly assigned. According to the techniques described in U.S. Pat. No. 4,598,960 a driver circuit in the form of an integrated circuit is mounted on a carrier board. The driver circuit interconnects with 64 etched output conductors on the carrier board as well as 10 input conductors. The carrier board is specially configured through the use of data apertures to align with correspondingly grouped row or column conductors of the electrophoretic display under such circumstances that the data apertures are aligned with mounting posts mated to the base plate of the assembly and insure appropriate alignment of the carrier boards. Connection of the carrier board outputs to the row and column conductors within the electrophoretic display is mechanically achieved through the us of Zebra connectors and this same technique is employed to provide connection to the inputs of the carrier board. Connection of the carrier board to the integrated circuit is achieved through wire bonding techniques and the entire assembly once fabricated is clamped in place to assure that once appropriate mechanical and electrical alignment is achieved the same will be retained.
While the techniques set forth in U.S. Pat. No. 4,598,960 are effective, they are subject to a number of difficulties and result in a display assembly which is complex, costly to fabricate, and subject to a number of reliability problems both during initial fabrication and after periods of use. For example, the ceramic carrier boards employed are costly and the data apertures provided therein must be accurate within one ten thousandth of an inch or else alignment problems may result. In addition, assembly of the complex structure is time consuming which increases manufacturing costs and the mechanical connections achieved with the Zebra connectors can be subject to reliability problems in the presence of substantial vibration as can the clamps employed.
Therefore, it is a principal object of the present invention to provide improved monolithic flat panel display apparatus and methods for the fabrication thereof.
A further object of this invention is to provide electrophoretic display apparatus and methods for the fabrication of the same wherein row and column driver circuits are directly bonded to the display panel and connected to individual conductors therein through use of wire bonding techniques.
An additional object of the present invention is to provide electrophoretic display apparatus and methods therefor wherein portions of the row and column conductors are patterned and metalized to permit the same to be directly bonded to driver circuits.
Various other objects and advantages of the present invention shall become clear from the following detailed description of an exemplary embodiment thereof and the novel features will be particularly pointed out in conjunction with the claims appended hereto.